Viscometer

Abstract

A viscometer wherein a sample of the material to be tested is introduced into the annular clearance between a stationary cylinder and a vertical shaft which carries several weights. As the shaft descends at a speed which is a function of the combined mass of weights and the viscosity of the sample in the clearance, successive weights are automatically detached from the shaft, either by piling up on top of each other after the lowermost weight comes to rest on a platform, or by being intercepted by plates which are mounted at different levels. Means is provided for centering the weights prior to start of a multi-stage test and for returning the shaft and the weights to starting positions upon completion of a multi-stage test.

What is claimed is: 
     
       1. In a viscometer for testing the rheological properties of materials which are flowable at least in response to the application of deforming stresses thereto, the combination of a stationary first measuring element; a vertically movable second measuring element adjacent to and defining with said first element a clearance for reception of a sample of the material to be tested, such material being subjected to a shear stress during vertical movement of said second element; and means for moving said second element vertically, including at least two discrete weights, means for connecting said weights to said second element so as to move the latter vertically with a predetermined force, and means for disconnecting at least one of said weights from said second element after elapse of an interval during which said second element moves through a predetermined distance so that said force is reduced accordingly in response to disconnection of said one weight. 
     
     
       2. The combination of claim 1, wherein said second element has a lower end portion and said connecting means includes means for securing the other of said weights to said lower end portion, said one weight being suspended on and being normally spaced apart from said other weight and said other weight being movable toward said one weight when the latter is held against downward movement, said disconnecting means including a stop located below said one weight so that the latter comes to a rest on said stop after said second element descends through said distance while said other weight is free to descend toward the thus arrested one weight. 
     
     
       3. The combination of claim 2, wherein the downward movement of said second element is terminated when said other weight reaches and comes to rest on the arrested one weight. 
     
     
       4. The combination of claim 2, further comprising means for centering said other weight with respect to said second element prior to vertical movement of said second element. 
     
     
       5. The combination of claim 4, wherein said centering means is movable to and from an upper end position and includes means for lifting said other weight and said second element to a starting position prior to testing of a fresh sample in said clearance, and further comprising means for moving said centering means to said starting position and for thereupon permitting said centering means to descend faster than said other weight and said second measuring element. 
     
     
       6. The combination of claim 5, wherein said last mentioned moving means comprises a crank arm rotatable about a horizontal axis and movable to and from an upper dead center position in which said second element is held in said starting position. 
     
     
       7. The combination of claim 2, wherein the normal spacing of said weights at least equals a distance which is required to ascertain the velocity of the second element before said one weight reaches said stop. 
     
     
       8. The combination of claim 2, further comprising means for coupling said one weight with said other weight, said coupling means including a rod having an end portion secured to one of said weights and being reciprocable in the other of said weights to the extent which is necessary to enable said first mentioned other weight to come to rest on said first mentioned one weight on further downward movement of said second element subsequent to stoppage of said first mentioned one weight. 
     
     
       9. The combination of claim 8, wherein said rod includes a head at the other end thereof and said last mentioned other weight has an end wall with a bore large enough for the major portion of said rod but preventing the extraction of said head from the interior of said last mentioned other weight. 
     
     
       10. The combination of claim 9, wherein said rod has an enlarged portion which is adjacent to said head and is snugly received in said bore when said weights are disposed at a maximum distance from each other. 
     
     
       11. The combination of claim 1, further comprising means for balancing the weight of said second measuring element so that the weight of such element does not influence the rate of vertical movement thereof. 
     
     
       12. The combination of claim 11, further comprising at least one pulley disposed above said first element and a cable trained over said pulley and having a first portion disposed at one side of said pulley and connected to said second measuring element and a second portion at the other side of said pulley, said balancing means including a counterweight attached to said second portion of said cable. 
     
     
       13. The combination of claim 12, wherein said second measuring element comprises an upper end portion consisting of magnetizable material and further comprising a permanent magnet attached to said first portion of said cable, said end portion of said second element adhering to said magnet. 
     
     
       14. The combination of claim 1, wherein said first element includes a cylinder having an upright cylindrical hole and said second measuring element is a shaft which is reciprocable in said hole. 
     
     
       15. The combination of claim 1, wherein said second measuring element is flexible. 
     
     
       16. The combination of claim 1, wherein said second element is a rigid shaft having an upper end portion above said clearance and said weights are mounted on the upper end portion of said second element. 
     
     
       17. The combination of claim 16, wherein said one weight is disposed above said other weight and said disconnecting means comprises a device arranged to intercept said one weight after said second element decends through said distance. 
     
     
       18. The combination of claim 1, further comprising at least one auxiliary weight and means for connecting said auxiliary weight to one of said first mentioned weights. 
     
     
       19. The combination of claim 1, wherein the resultant force which said weights apply to said second element acts in the axial direction of said second element. 
     
     
       20. The combination of claim 1, further comprising means for movably coupling said weights to each other and at least one auxiliary weight having a slot for said coupling means and means for attaching said auxiliary weight to one of said first mentioned weights. 
     
     
       21. The combination of claim 20, further comprising at least one additional weight provided on said auxiliary weight. 
     
     
       22. The combination of claim 20, wherein said auxiliary weight is an annulus and said slot extends substantially radially of said annulus, said annulus further having a cutout disposed substantially diametrically opposite said slot. 
     
     
       23. The combination of claim 20, wherein said attaching means comprises a bayonet lock.